1. Field of the Invention
The present invention relates to a musical tone synthesizing apparatus which is applicable to synthesis of the musical tones of plucked stringed instruments, percussion type stringed instruments and other musical instruments of this type.
2. Prior Art
Devices are well known wherein, through simulation of the tone generation mechanisms of an acoustic musical instrument, the sound of these acoustic musical instruments can be synthesized.
As an example, devices for synthesis of the sound of stringed instruments have been described, consisting of a low-pass filter for simulating reverberation losses in the strings, and a delay circuit for simulating propagation delays of the vibration of the strings, the low-pass filter and delay circuit being connected so as to form a closed loop. With such a device, an excitation signal, for example an impulse signal, is introduced into the closed loop. Thus introduced, the impulse signal circulates about the closed loop with a period equal to the frequency at which the strings under simulation would vibrate in the actual stringed instrument. The bandwidth of the signal is restricted each time it traverses the low-pass filter, and finally, the signal is output from the closed loop as a signal corresponding to the tone of the stringed instrument being synthesized.
with the device described above, by adjusting the delay period of the delay circuit and the characteristics of the low-pass filter, the sound of a plucked stringed instrument such as a guitar, or of a percussive stringed instrument such as a piano can be synthesized, having characteristics very close to those of the target instrument. When simulating the sound of a stringed instrument played with a bow such as a violin, the excitation signal is introduced into the closed loop from an excitation circuit, wherein a signal is generated simulating the effect of the bow. Examples of this type of musical tone synthesizing apparatus include those disclosed in Japanese Patent Application, Laid-open No. 63-40199 and U.S. Pat. No. 4,130,043.
With the conventional musical tone synthesizing device described above, each closed loop formed by the low pass filter and delay circuit is only capable of synthesizing the sound of one string at any given moment. Thus, these conventional devices model an instrument for which only one string is struck, plucked, or otherwise caused to vibrate at one time. For the above reason, such a device cannot realized the sound effect of, for example, an acoustic piano of which three strings corresponding to one of lower keys are struck at one time, wherein each strings being tuned so as to create slight discrepancies in tuning between each of the three strings to thereby realize beat effect. The above described conventional devices would of course not be able to simulate such an effect. Thus these devices are considerably limited in their ability to faithfully reproduce the sound of various conventional stringed instruments.